Thank you for your reply - it was a relief to have our suspicions confirmed - we thought the problems were to do with it not being level. In fact if anything it is getting noisier! It is not hugely out but using a spirit level you can clearly see it isn't level. The mystery of why we were told that we were having a new boiler only to find it was the same one however still rolls on. We have written/emailed to the plumber and asked him to come and explain. We wait with bated breath....